Method and apparatus for stripping sulfur-containing compounds from hydrocarbon feed stock in hydrorefining of petroleum distillates

ABSTRACT

A unit for hydrorefining of hydrocarbon crude oil comprising sulfur-containing compounds comprises first catalyst layer  33  and second catalyst layer  38 , top space  34  for separating vapor component and liquid component, bottom space  36 , and valve tray  35  that divides top space  34  and bottom space  36 . Hydrogen released from hydrogen nozzle  40  placed in the bottom space is passed through liquid component that has accumulated in the valve tray and stripping of liquid components is performed. Hydrogen released from hydrogen nozzle  40  is again introduced, to second catalyst layer  38  as a cocurrent with the stripped liquid component. By stripping, it is possible to reduce the sulfur content, the nitrogen content and reduce the aromatic content of the hydrocarbon crude oil when compared to the conventional method. Since the hydrorefining unit has a simple structure, the unit can be easily made by modifying existing units.

This application is the national phase under 35 U.S.C. § 371 of PCTInternational Application No. PCT/JP00/00147 which has an Internationalfiling date of Jan. 14, 2000, which designated the United States ofAmerica and was not published in English.

TECHNICAL FIELD

The present invention relates to hydrorefining of petroleum middledistillate, such as kerosene, gas oil, and particularly, to ahydrorefining apparatus and hydrorefining method for obtainingsuper-low-sulfur middle distillates with a sulfur content of 150 ppm orless.

BACKGROUND ART

A method for hydrorefining crude oil by mixing the crude oil withhydrogen, heating and bringing into contact with hydrorefining catalystsloaded in multiple catalyst layers is known as a typical hydrorefiningmethod for obtaining low-sulfur gas oil with a sulfur content of 500 ppmor less. In this method, there are also cases wherein hydrogen isfurther introduced between the multiple catalyst layers. However, theconcentration of impurities, such as hydrogen sulfide, ammonia, etc.,produced by hydrorefining contained in the hydrorefined hydrocarbonsnear the outlet of the catalyst layers rises and therefore,hydrorefining wherein contents of the sulfur and nitrogen are adequatelyreduced is difficult. The hydrogen sulfide, ammonia, etc., inhibitcatalytic reaction and as a result, activity of the catalyst is markedlyreduced. Consequently, as disclosed in U.S. Pat. Nos. 5,705,052 and5,720,872, hydrogen sulfide and ammonia gas that have been dissolved inthe hydrorefined hydrocarbons are stripped inside a vessel separate fromthe reaction column in which the catalyst layers have been set up.

With this type of hydrorefining unit, hydrogen and feed oil are broughtinto contact with catalyst as a cocurrent. The method is known wherebythe hydrogen sulfide and ammonia impurities dissolved in the effluentare removed by allowing hydrogen to flow into the catalyst as acountercurrent to the liquid hydrocarbons (feed oil) that flow throughthe catalyst, as described in, for instance, Japanese Patent No.2,617,158.

However, it is difficult to hydrorefine gas oil distillates in order tobring the sulfur content to 150 ppm or less, particularly 50 ppm orless, with the above-mentioned conventional unit and method. Inparticular, there is a problem that the allowable range of the gasquantity of flow and feed oil quantity of flow with which stableoperation is possible is narrow in hydrorefining units with which thepreviously mentioned hydrogen and feed oil are brought into contact withcatalyst as cocurrent and therefore, operation is not simple.

SUMMARY OF THE INVENTION

The first object of the present invention is to provide a hydrorefiningmethod which can make sulfur content, nitrogen content, and aromaticcontent lower than with conventional hydrorefining methods.

The second object of the present invention is to provide a hydrorefiningunit with a simple structure, and that can be made by simplemodification of existing hydrorefining units.

In accordance with the first aspect of the present invention, ahydrorefining unit for hydrorefining hydrocarbon feed oil containingsurfur-containing compounds is provided, which comprises a firstcatalyst layer and a second catalyst layer; a holding member positionedbetween the first catalyst layer and the second catalyst layer fortemporarily holding the liquid component that flows out from the firstcatalyst layer; a hydrogen feed source; and a hydrogen introduction partconnected with the hydrogen feed source for simultaneously introducinghydrogen from the hydrogen feed source to the liquid component that hasbeen held in the holding member and the second catalyst layer.

With the hydrorefining unit of the present invention, liquid componentflowed out from the first catalyst layer is held by a holding memberprovided between the first catalyst layer and the second catalyst layerand the hydrogen sulfide and ammonia in the liquid component can bestripped by introducing hydrogen from the hydrogen introduction part tothis liquid component held in the holding member. As a result of thisstripping, hydrorefining in the second catalyst layer can be started inan ambient atmosphere that does not comprise impurities such as hydrogensulfide, ammonia, etc., and a hydrorefined product with a super-lowsulfur content, super-low nitrogen content, and low aromatic content canbe obtained. Hydrogen from the hydrogen introduction part also can befed to the second catalyst layer. Therefore, with the unit of thepresent invention, it is possible to simultaneously feed hydrogen forstripping and hydrogen for hydrorefining at the second catalyst layerfrom the hydrogen feed source. Consequently, impurities such as hydrogensulfide, ammonia, etc., can be easily removed using a simple unitstructure.

It is preferred that the hydrogen introduction part of the unit of thepresent invention be arranged on the downstream side of the holdingmember and on the upstream side of the second catalyst layer. Byarranging the hydrogen introduction part in this way, some of thehydrogen that has been introduced can rise to the holding member, whilethe remainder of the hydrogen can move toward the second catalyst layertogether with liquid component that has flown out from the holdingmember.

It is preferred that the first catalyst layer, second catalyst layer,and holding member of the unit of the present invention be housed in asingle reaction vessel. When constructed in this way, the unit of thepresent invention can be made easily by modifying ordinary hydrorefiningunits with a first catalyst layer and a second catalyst layer. In thiscase, the hydrogen introduction part can be provided between the holdingmember and the second catalyst layer.

The above-mentioned holding member may be a tray having a discharge holefor liquid component and in which the liquid component accumulates. Itcan be, for instance, a valve tray, a sieve tray, or a cap tray. Theabove-mentioned holding member may also be a packing material throughwhich the liquid component can pass.

In accordance with the second aspect of the present invention, a methodfor hydrorefining hydrocarbon feed oil comprising a sulfur-containingcompound using at least two catalyst layers is provided, which comprisesthe steps of introducing hydrocarbon feed oil to the first catalystlayer together with hydrogen; stripping the liquid component that hasflown out from the first catalyst layer with the first hydrogen gasstream that is fed from the hydrogen introduction part; and introducingthe stripped liquid component to the second catalyst layer together withthe second hydrogen gas stream that is fed from the hydrogenintroduction part.

By means of the present invention, hydrogen for stripping and hydrogenfor hydrorefining can be shared and therefore, it is possible to make ahydrorefining plant with a simple structure and at low cost.

The above-mentioned hydrogen introduction part can be provided between afirst catalyst layer and a second catalyst layer in the method of thepresent invention. Moreover, it is preferred that the liquid componentflowing out from the first catalyst layer be temporarily held in theholding member. In this case, the first hydrogen gas stream and thesecond hydrogen gas stream can be introduced between the above-mentionedholding member and the second catalyst layer.

The second hydrogen gas stream can be introduced to the second catalystlayer together with the stripped liquid component and as a cocurrent tothe above-mentioned liquid component. It is preferred in the presentinvention that the hydrocarbon feed oil be hydrocarbon oil with a 90%distillation temperature of 250° C. or higher.

The method of the present invention can further comprise removing thevapor component produced from the first catalyst layer and the vaporcomponent produced by stripping. Vapor component comprising impurities,such as hydrogen sulfide, ammonia, etc., is removed from the product ofthe first catalyst layer and the liquid component is again stripped withfresh hydrogen. Therefore, hydrorefining in the second catalyst layercan be performed in an ambient atmosphere that does not compriseimpurities such as hydrogen sulfide, ammonia, etc., to obtain ahydrorefined product with a super-low sulfur content, super-low nitrogencontent, and low aromatic content.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an explanatory view that explains the hydrorefining unitaccording to an embodiment of the present invention.

FIG. 2 is a cross sectional view that describes part of the reactionvessel of the embodiment.

FIG. 3 is a cross sectional view that describes an embodiment of adifferent form of the part of the reaction vessel in FIG. 2.

FIG. 4 is a cross sectional view that describes an embodiment of yetanother different form of the part of the reaction vessel in FIG. 2.

BEST MODE FOR CARRYING OUT THE INVENTION

[Feed Oil]

The hydrocarbon feed oil, as used in the present invention, is feed oilthat has been obtained via hydrorefining processes, such as distillationfrom petroleum and coal liquefaction oil, etc., which may be petroleumsubstitute. For example, it is preferred that middle distillate productsand gas oil bases for diesel fuel with a 90% distillation temperature of250° C. or higher, particularly 300 to 400° C., be used. The typicalproperties of gas oil for diesel fuel are a 10% distillation temperatureof 220 to 300° C., a 50% distillation temperature of 260 to 340° C., anda 90% distillation temperature of 320 to 380° C. Direct light oildistillate obtained by atmospheric distillation of crude oil, thermalcracking oil which is the light distillate obtained by a reaction whichis mainly a radical reaction wherein heat is applied to heavydistillate, catalytic cracking oil which is obtained when middledistillates and heavy distillates are catalytically cracked by a zeolitecatalyst can be used. Furthermore, the distillation temperature is thevalue from JISK 2254 “Fuel Oil Distillation Testing Methods.”

[Filler Hole for Feed Oil and Hydrogen]

A filler hole for feed oil and hydrogen is provided at the upstream partof the hydrorefining vessel used in the present invention. Separatefiller holes for feed oil and hydrogen can also be provided, but amixture of the feed oil and hydrogen is usually heated and introduced tothe reaction vessel.

[Catalyst Layer]

At least two fixed bed catalyst layers are used in the presentinvention. These may be kept in multiple reaction vessels, but it ispreferred that they be kept in a single reaction vessel.

The catalyst used in the first catalyst layer and second catalyst layerpreferably comprises approximately 5 to 30 wt % in terms of metalelement of at least one type of Periodic Table Group 6 metal element,particularly molybdenum or tungsten, and a total amount of 1 to 10 wt %in terms of metal element of at least one type of Group 8 non-noblemetal element, particularly either nickel or cobalt or both, supportedon an alumina carrier. It is preferred that a catalyst be used whereinin addition to these metals, 0.1 to 8 wt % phosphorus in terms ofphosphorus element is supported. In addition to alumina, the carrier mayalso comprise compound oxides with high acidity, such as silica alumina,titania alumina, zeolite, etc., and a Group 8 noble metal element mayalso be supported as the metal component.

[Holding Member]

The unit of the present invention has a holding member positionedbetween the first catalyst layer and the second catalyst layer fortemporarily holding the liquid component that has flown out from thefirst catalyst layer. The holding member can be, for instance, a tray,such as a valve tray, a sieve tray, a cap tray, etc., set up in thespace between the two catalyst layers. The liquid phase hydrocarbon oilcan stay in this tray and the vapor component present in the top spaceof the tray is kept from passing to the bottom space of the tray by thishydrocarbon oil that stays in the tray, while the vapor component in thebottom space of the tray can pass to the top space of the tray. Apacking bed that has been packed with a packing material, such asRaschig rings, etc., can be provided in place of the above-mentionedtray for accumulation of the liquid. Furthermore, the holding memberalso functions as a separation means that separates the vapor componentand the liquid component that have passed through the first catalystlayer.

Impurities, such as hydrogen sulfide and ammonia, etc., can be removedfrom the liquid component by feeding hydrogen gas to the liquidcomponent that has accumulated in the above-mentioned holding member andstripping the liquid component of impurities. It is preferred that ameans for adjusting the pressure of the top space and/or the bottomspace of the holding member be added in order to adjust the quantity offlow of hydrogen gas for stripping. Controlling extraction of vaporcomponent from the top space, or controlling the amount of hydrogenintroduced to the bottom space, so that the quantity of flow ofstripping gas is constant can be used as such an adjusting means.

[Stripping]

The hydrocarbon oil that is held or stays on the holding member isstripped by hydrogen. Stripping is preferably performed by introducinghydrogen in the form of bubbles from the base of the hydrocarbon oillayer. The hydrogen that is introduced preferably has a low hydrogensulfide concentration of usually 500 volume ppm or less, particularly100 volume ppm or less.

[Top Space]

There is a top space (also referred to as separation space) between theholding member and the first catalyst layer. Of the hydrocarbons,hydrogen, hydrogen sulfide, ammonia, etc., that flow out from the firstcatalyst layer, the liquid component stays on the holding member, whilethe vapor component fills the top space. Moreover, the hydrogen that hasstripped the liquid component and the vapor component produced by thesame stripping in the holding member also flow into the top space.

[Gas Discharge Hole]

A gas discharge hole is formed in the top space for guiding the vaporcomponent that is fills the top space to the outside (also referred toas “gas outlet”). The gasified hydrocarbons, hydrogen, hydrogen sulfide,ammonia, etc., are removed from the discharge hole. The removed vaporcomponent is usually cooled to liquefy the hydrocarbon oil and isolatethe hydrocarbon oil from hydrogen comprising impurities such as hydrogensulfide, ammonia, etc., and hydrocarbon gases, such as methane. Theseparated hydrogen is recycled after impurities such as hydrogensulfide, ammonia, etc., are removed therefrom.

[Bottom Space]

A bottom space is provided between the holding member and the secondcatalyst layer. A hydrogen introduction part is set up in the bottomspace and hydrogen is introduced from the hydrogen introduction part tothe bottom space. This hydrogen is used for stripping at the holdingmember, or it is mixed with the hydrocarbon oil that flows down from theholding member into the second catalyst layer. It is preferred that adispersion means, such as a distributor tray, be provided in between thehydrogen introduction part and the second catalyst layer in order toprovide uniform flow to the second catalyst layer.

[Product Outlet]

A product outlet is provided at the bottom of the second catalyst layer.Hydrogen comprising hydrogen sulfide, etc., and hydrorefined hydrocarbonoil flow out from the second catalyst layer and these products areusually cooled and separated into hydrogen gas comprising hydrogensulfide and hydrocarbon oil. The hydrogen sulfide, etc., is removed fromhydrogen comprising hydrogen sulfide that has separated and the purifiedhydrogen is recycled.

[Reaction Vessel]

In the present invention, the two catalyst layers, holding member,filler hole, top space, bottom space, gas discharge hole, hydrogenintroduction part, product outlet, etc., may be stored in multiplevessels, but it is preferred that they be housed in one vessel. It isparticularly preferred that when a modified ordinary reaction vessel isused, a single through hole be made in the reaction vessel wall and thatthis through hole be continuous with the gas discharge hole and thehydrogen introduction part. By providing the single through hole, it isenabled to reduce the number of parts of the reaction vessel to bemodified. When an ordinary reaction vessel has a through hole forintroduction of hydrogen for cooling, the gas discharge hole andhydrogen introduction part can be connected with this through hole,whereby a modification processes to form a new through holes can beomitted.

[Hydrorefining]

In the operating conditions for hydrorefining according to the presentinvention, a liquid space velocity of 0.1 to 10 [hr⁻¹], preferably 0.1to 2.0 [hr⁻¹], a hydrogen/oil ratio of 100 to 2,000 [L/L], preferably200 to 500 [L/L], and a hydrogen pressure of 20 to 200 kg/cm²,preferably 40 to 100 kg/cm² are used. The reaction temperature dependson the catalyst that is used, but is usually 220 to 450° C.,particularly 300 to 400° C.

When light oil base distillate is hydrorefined according to the presentinvention, the sulfur content becomes 150 ppm or less, preferably 50 ppmor less. It is further possible to bring the sulfur content to 150 ppmor less, total aromatic content to 25 vol % or less, particularly 20 vol% or less, and the aromatic content of 2-rings or more to 2 vol % orless, particularly 1 vol % or less. In addition, the nitrogen contentcan usually be brought to 1 ppm or less, and the aromatic content of3-rings or more can be brought to 0.2 vol % or less, particularly 0.1vol % or less.

The hydrogen used for stripping in the present invention may be gas thatcomprises hydrogen as the main component, and it can be a mixed gascomprising 80 to 90 molar % hydrogen, such as a mixed gas with methane.

EMBODIMENTS

Embodiments of the hydrorefining unit and the hydrorefining method ofthe present invention will be described in concrete terms below inreference to the drawings, but the present invention is not limited tothe embodiments.

Embodiment 1

In the hydrorefining unit in FIG. 1, feed oil 10 is pressurized withpump 11, preheated by heat exchanger 12, mixed with hydrogen gas 20, andthen heated by heater 13 to the temperature needed for hydrorefining.The mixed fluid consisting of the heated feed oil and hydrogen gas isfed to filler hole 31 formed at the top end of cylindrical reactionvessel 30, uniformly dispersed by first distributor tray 32, anddescends to first catalyst layer 33 loaded with hydrorefining catalyst.The feed oil in the mixed fluid is partially hydrorefined in thepresence of hydrogen and the same intermediate product flows out fromthe bottom end of first catalyst layer 33.

Valve tray 35 is provided at the bottom of first catalyst layer 33 withtop space 34 interposed therebetween. Of the intermediate product thathas flowed out from the bottom end of first catalyst layer 22, the vaporcomponent accumulates in the top space, while the liquid componentaccumulates in valve tray 35. Structure of the valve trays will bedescribed later.

Second distributor tray 37 is provided underneath valve tray 35 withbottom space 36 interposed therebetween. Hydrogen gas is introduced tobottom space 36 by hydrogen gas nozzle 4, which is the hydrogen gasintroduction part. Some of the hydrogen gas that has been introducedrises to become bubbles in the liquid component on valve tray 35 andcomes into contact as a countercurrent to the liquid component that hasaccumulated on the tray so that the vapor component, such as hydrogensulfide, etc., contained in the liquid component is stripped. The gasused for stripping is mixed with vapor component from first catalystlayer 33 in top space 34. Extraction nozzle 50, which serves as the gasdischarge hole, is provided in top space 34 so that the mixed vaporcomponent is extracted to outside reaction vessel 30.

The liquid component that has been stripped flows out from valve tray 35to bottom space 36, is mixed with hydrogen gas from hydrogen nozzle 4and descends to second catalyst layer 38 loaded with hydrorefiningcatalyst through second distributor tray 37. The liquid component isfurther hydrorefined in the presence of hydrogen and its product flowsout from the bottom end of second catalyst layer 38 and is removed fromguide opening 39 provided at the bottom end of reaction vessel 30.

The removed product is cooled by feed oil in heat exchanger 12 andfurther cooled by heat exchanger 60. The cooled product is fed tohigh-pressure separation cell 61. The hydrorefined liquid component isremoved from base 62 of high-pressure separation cell 61 as product oil64. Moreover, the component extracted from extraction nozzle 50 is alsoliquefied to become product oil 64.

The vapor component extracted from extraction nozzle 50 is cooled byhydrogen gas 20 in heat exchanger 51 and further cooled in heatexchanger 52 and fed to high-pressure separation cell 53. Of theextracted vapor component, the hydrorefined hydrocarbon oil is liquefiedby cooling and removed from base 54 of high-pressure separation cell 53to become product oil 64. Moreover, when necessary, part of thishydrocarbon oil can be pressurized by pump 58, introduced to hydrogennozzle 40, and fed to the second catalyst layer through seconddistributor tray 37 in order to improve desulfiding activity.

Of the extracted vapor component, the hydrogen component comprisinghydrogen sulfide, etc., is removed from over head 55 of high-pressureseparation cell 53 and sent to hydrogen recycling unit 21 via flow meter56 and flow adjustment valve 57. Stripping in valve tray 35 can beadjusted by adjusting the quantity of flow of this hydrogen component.Flow adjustment valve 57 is controlled in accordance with the indicationon flow meter 56 so that quantity of flow is brought to the quantity offlow with which adequate stripping is possible.

The hydrogen component comprising hydrogen sulfide, etc., is sent fromover head 55 of high-pressure separation cell 53, or from over head 63of high-pressure separation cell 61, to hydrogen recycling unit 21.Hydrogen from which impurities such as hydrogen sulfide, etc., have beenremoved by hydrogen recycling unit 21 is pressurized by compressor 22 asrecycled hydrogen. Some of the pressurized recycled hydrogen is mixedwith make-up hydrogen 23 obtained by the hydrogen production process(not shown) and sent from hydrogen nozzle 40 to bottom space 36. Thishydrogen is used for stripping in valve tray 35 and hydrorefining atsecond catalyst layer 38.

The remainder of the pressurized recycled hydrogen becomes hydrogen gas20 that has been preheated by heat exchanger 51 and is mixed withpreheated oil 10 and used for hydrorefining at first catalyst layer 33.

The structure near valve tray 35 will be further explained using FIG. 2.Catalyst particles are held by tray 33 a at the bottom end of firstcatalyst layer 33 inside reaction vessel 30 and valve tray 35 is placedunderneath the same. Valve tray 35 is obtained by forming multipleholes, which serve as the discharge holes for liquid component, indiaphragm 35 a, and a valve 35 b is provided slidably in each of theholes. When each valve 35 b is lifted up by the pressure of the hydrogenthat has been fed from nozzle 40 into bottom space 36, gaps are formedbetween valves 35 b and diaphragm 35 a. The hydrogen gas passes fromthese gaps through liquid layer 100, which consists of liquid componentaccumulated on valve tray 35, and floats up. As a result, the liquidcomponent is stripped by hydrogen gas with good efficiency. In themeantime, the liquid component falls through these gaps into bottomspace 36.

Extraction nozzle 50, with which the hydrogen gas used in stripping andthe vapor component that flows out from first catalyst layer 33 areremoved from reaction vessel 30, runs through a side wall of reactionvessel 30 and opens at top space 34. Hood 50 a is provided above theopen part of extraction nozzle 50 so that liquid component ofintermediate product will not directly enter the opening.

Hydrogen nozzle 40 for feeding the hydrogen used in stripping on valvetray 35 and in hydrorefining at second catalyst layer 38 runs throughthe side wall of reaction vessel 30 at bottom space 36 underneath valvetray 35. Hydrogen nozzle 40 is a tube having many openings in its sidewalls. It diffuses and injects hydrogen gas into bottom space 36 so thatit comes into uniform contact with the liquid component that has passedthrough valve tray 35.

This liquid component accumulates on second distributor tray 37, thequantity of flow becomes uniform, and the liquid component is fed tosecond catalyst layer 38. Second distributor tray 37 has a structurewherein multiple chimneys 37 d are provided on diaphragm 37 a. Eachchimney 37 b is cylindrical and opening 37 d is formed in its side wall.Therefore, the liquid component that has accumulated in the chimneysuniformly flows from the same openings 37 d to second catalyst layer 38.Hood 37 c is provided above chimney 37 b so that he liquid componentthat has passed through valve tray 35 does not directly reach secondcatalyst layer 38.

Embodiment 2

Another embodiment of the hydrorefining unit of the present inventionwill now be described in concrete terms using FIG. 3. The structure nearvalve tray 35 shown in FIG. 3 is approximately the same as the structureshown in FIG. 2, but it differs in terms of the arrangement ofextraction nozzle 50. Extraction nozzle 50 in FIG. 3 is introduced intoreaction vessel 30 via through hole 40 a which runs through the sidewall of reaction vessel 30, and further extends to top space 34 throughdiaphragm 35 a of valve tray 35. When this type of structure isemployed, the number of through holes leading to reaction vessel 30 canbe reduced and therefore, the unit of the present invention can beobtained easily by modifying an ordinary reaction vessel used inhydrorefining.

Embodiment 3

A modified hydrorefining unit of the present invention will now bedescribed using FIG. 4. The hydrorefining unit in FIG. 3 is the same asthe unit in Embodiment 1 with the exception that the valve tray in FIGS.1 and 2 has been changed to packing material layer 110. Raschig ringspacked on top of a base with multiple openings can be used as packinglayer material 110. When the liquid component that flows out from firstcatalyst layer 33 passes through packing layer 110, it comes intocontact as a countercurrent with the hydrogen that is rising up frompacking material layer 110 and stripping is thereby performed with goodefficiency.

The hydrorefining unit and method of the present invention have beenexplained in concrete terms with embodiments, but the present inventionis not limited to these embodiments and can comprise various changes andmodifications conceived of by a person skilled in the art. Hydrogennozzle 40 was placed in the space underneath valve tray 35 inEmbodiments 1 and 2, but a plate with hydrogen nozzle spray holes thatserve as the hydrogen introduction part can be provided at the sameposition in place of valve tray 35. This plate has a hydrogen feed pathinside and multiple hydrogen spray holes joining with the hydrogen feedpath in the top and bottom surfaces of the plate. The hydrogen sprayholes made in the top surface of the plate can feed hydrogen forstripping to liquid component on the plate. The hydrogen spray holesformed in the bottom surface of the plate can feed hydrogen forhydrorefining to the second catalyst layer. Moreover, it is alsopossible to make multiple through holes in the plate so that they do notinterfere with the hydrogen feed path in the plate and thereby to allowthe liquid component to pass through these through holes and fall fromon top of the plate to the bottom space underneath the plate.

As another embodiment, it is also possible to make hydrogen nozzle 40shown in FIGS. 2 and 3 branch into a first tube and a second tube inbottom space 36 and place the first tube on diaphragm 35 a. Part of thehydrogen introduction part can also be provided inside the holdingmember. In this case, valves 35 b can be omitted. On the other hand, thesecond tube can be placed at the same position as hydrogen nozzle 40 inFIGS. 2 and 3.

1. A method for hydrorefining hydrocarbon feed oil including asulfur-containing compound using at least two catalyst layers,comprising the steps of: introducing hydrocarbon feed oil to the firstcatalyst layer together with hydrogen; temporarily holding, by using aholding member, a liquid component that has flown out from the firstcatalyst layer, and stripping the liquid component with a first hydrogengas stream that is fed from a hydrogen introduction part providedbetween the first catalyst layer and the second catalyst layer so thatthe first hydrogen gas stream passes through the liquid component as acountercurrent to the liquid component; removing a vapor component thathas been produced from the first catalyst layer and a vapor componentthat has been produced by stripping, while adjusting flow of the vaporcomponent produced from the first catalyst layer and the vapor componentproduced by stripping in order to perform the stripping; and introducingthe stripped liquid component to the second catalyst layer together withand cocurrent with a second hydrogen gas stream that is fed from thehydrogen introduction part.
 2. A hydrorefining method according to claim1, wherein the holding member is a tray which has a liquid dischargehole and in which liquid component accumulates.
 3. A hydrorefiningmethod according to claim 1, wherein the holding member is a packingmaterial through which the liquid component can pass.
 4. A hydrorefiningmethod according to claim 1, wherein the hydrocarbon feed oil ishydrocarbon oil in which 90 vol % distillation temperature is 250° C. orhigher.
 5. A hydrorefining method according to claim 1, wherein thehydrocarbon feed oil has a 10 vol % distillation temperature of 220 to300° C. and a 90 vol % distillation temperature of 320 to 380° C., andthe hydrorefined hydrocarbon feed oil has a sulfur content of not morethan 150 ppm.
 6. The hydrorefining method of claim 1, comprising thefurther step of recycling hydrogen recovered from the removed vaporcomponent into a hydrogen gas stream being introduced into the process.7. A hydrorefining method according to claim 1, wherein the holdingmember is a valve tray.
 8. A hydrorefining unit for hydrorefininghydrocarbon feed oil including sulfur-containing compounds, comprising:a first catalyst layer and a second catalyst layer; a holding memberpositioned between the first catalyst layer and second catalyst layerfor temporarily holding a liquid component that flows out from the firstcatalyst layer, wherein said holding member is a valve tray; a hydrogenfeed source; a hydrogen introduction part, that is connected to thehydrogen feed source, for simultaneously introducing hydrogen from thehydrogen feed source to the liquid component held in the holding memberand the second catalyst layer, wherein the hydrogen introduced from thehydrogen introduction part has a first hydrogen gas stream and a secondhydrogen gas stream; a separation space that is positioned at the bottomof the first catalyst layer for separation of vapor component and liquidcomponent; means for adjusting pressure of the separation space and/or aspace between the holding member and the second catalyst layer; and agas outlet through which the vapor component is discharged from theseparation space.
 9. A hydrorefining unit according to claim 8, whereinsaid means for adjusting pressure comprises a flow meter and flowadjustment valve that are operatively connected to said gas outlet. 10.A hydrorefining unit according to claim 8, further comprising means forrecycling hydrogen from the discharged vapor component into the hydrogenintroduction part.
 11. A hydrorefining unit according to claim 8,wherein the first catalyst layer, second catalyst layer, and holdingmember are housed in a single reaction vessel.
 12. A hydrorefining unitaccording to claim 8, wherein the holding member is a tray which has adischarge hole for liquid component and in which liquid componentaccumulates.
 13. A hydrorefining unit according to claim 8, whereinimpurities are stripped from the liquid component held in the holdingmember by the first hydrogen gas stream.
 14. A hydrorefining unitaccording to claim 13, wherein the impurities are hydrogen sulfideand/or ammonia.
 15. A hydrorefining unit for hydrorefining hydrocarbonfeed oil including sulfur-containing compounds, comprising: a firstcatalyst layer and a second catalyst layer; a holding member positionedbetween the first catalyst layer and second catalyst layer fortemporarily holding a liquid component that flows out from the firstcatalyst layer, wherein said holding member is a valve tray; a hydrogenfeed source; a hydrogen introduction part, that is connected to thehydrogen feed source, for simultaneously introducing hydrogen from thehydrogen feed source to the liquid component held in the holding memberand the second catalyst layer; a separation space that is positioned atthe bottom of the first catalyst layer for separation of vapor componentand liquid component, wherein the separation space and/or a spacebetween the holding member and the second catalyst layer can have itspressure adjusted; and a gas outlet through which the vapor component isdischarged from the separation space.
 16. A hydrorefining unit accordingto claim 15, comprising a flow meter and flow adjustment valveoperatively connected to said gas outlet for the adjustment of pressurein the separation space and/or the space between the holding member andthe second catalyst layer.
 17. A hydrorefining unit according to claim15, further comprising means for recycling hydrogen from the dischargedvapor component into the hydrogen introduction part.